Albumin concentration and colloid osmotic pressure of interstitial fluid collected by wick technique from rat skeletal muscle. Evaluation of the method.

Abstract

Interstitial fluid from rat skeletal muscle has been collected by multifilamentous nylon wicks. The wicks consisted of 5-600 single filaments and had an overall diameter of 1-2 mm. The wicks were implanted in the muscle by means of a mending needle. The wicks were removed at various times after implantation, and colloid osmotic pressure (COP) or albumin concentration in wick fluid was measured. The fluid contained in the wick had a COP of 8-10 mmHg and an albumin concentration about 1/3 that of plasma. COP in wicks preloaded with serum of serum/saline dilution was higher after 1/2 and 1 h of implantation, but was nearly identical to that of saline soaked wicks after 2 h implantation. Intravenous injection of labelled albumin showed that wick implantation caused a marked leakage of proteins from plasma to the wick. However, 1/2 to 1 h after implantation the leakage was markedly reduced. The initial leakage of albumin could be diminished with protease inhibitor (aprotinin), but not with prostaglandin-, serotonin-, or histamine antagonists. The experiments show that wick fluid colloid osmotic pressure reflects interstitial fluid colloid osmotic pressure, while the protein composition of wick fluid may not be identical to that of undisturbed interstitial fluid.